Well pumping system



Nov. 10, 1931. F. w. HILD WELL PUMPING SYSTEM Filed March l5, 1928 2shee's-sheet 1 INVENTOR ATORNEY Nov. 10, 1931-. F. w. HILD 1,830,941

WELL PUMPING SYSTEM Filed March 15. 1928 2 Sheets-Sheet 2 INVENTORAT'TORNEY Patented Noir'. .10, 1931 W. BILD, F LOS ANGELES, CALIFORNIAwenn PUMPING sYs'riun Application led March 15, 1928. Serial No.261,808.

This invention relates generally to pumping systems and moreparticularly to longstloke pumping systems for oil wells and the li e.In my copending application, Serial No.

193,224, filed May 21, 1927, I have shown a long-stroke umpin systemcomprising apparatus an contro which is particularly adapted to be,utilized for pumping oil wells and the like, wherein a pair of motorsare connected to two sun-gears, or end elements, of a planetary gearsystem forming a differential gear set. The. middle element, or

planetary member, of the differential gear set is connected to operate acable winding drum, which actuates a cable that is connected to a pumpplunger. A reciprocatory motion is imparted to the plunger byperiodically reversing the direction of rotation of the drum. In thisparticular instance, the reversing of the drum is eiected by alternatelychanging the relative speeds of the motors.'

My copending application, Serial No. 221,-

418, filed September 23, 11927, shows another long-stroke pumping systemwherein a special form of diierential gear transmission with a singledriving motor is utilized to actuate a cable winding drum to which thepump plunger is connected. In this instance, reversal of the drum isefected by reversing the direction of rotation ofthe motor by means ofan oscillator mechanism interposed between the drum and a reversing typecontroller.

The present invention provides a longstroke pumping system embodying apart of v the apparatus shown in the latter application,

and additional apparatus that will be described in detail in thesubsequent paragraphs of this specification. v

Among the many important problems confronting the oil industry is thatof economically and eiiiciently pumping the deep wells that are now inuse. There are two general methods of obtaining oil from the ground,one, mechanical pumping, the other, raising the oil by compressed gas orair.

, Mechanical pumping is in greater use and is in general, the moreeconomical method. Long-stroke mechanical pumping systems, as providedin the hereinbeforc mentioned copending applications, eliminates manyofthe di'liculties and improves the eiii'ciencyof mechanical oil pumpingsystems.

The hazard of back pressure on the produc` ing sands inherent in the asor air lift, is

Y. not present'with mechanica pumping which on the contrary augments thenatural iiow 'oir' the iiuid into the well by exerting suction action. vThe difficulties due to variable and uncertain submergence attendantupon the gas lift'- method are absent from mechanical pumping.

On the other hand, the gas lift increases the recovery of naturalgasoline. Furthermore, the gas lift can continuously apply its liftingpower, whereas the single acting. mechanical pump is limited to one halfthe time, namely the lifting stroke.

It is the object of this invention' to` provide a pumping systemcombining the best features of the gas lift and the mechanical pump andwhich shall have mutual and automatic control of both.

-The introduction of compressed gas ata point below the fluid level in awell, results in apparently stretching the Huid column withoutincreasing its weight, by converting the fluid into a chain of bubblesreaching to the discharge line at the surface. Conse- A quently in thepumping system of this invens tion, the weight to be moved and hence thmsize and strength required of the mechanical pumping means will begreatly lessened.

Another object of the invention is to provide for controlling theoperation of a reciprocatory pump plunger by means of an auxiliary workdevice connected in the pumping system and disposed to be driven by theenergy stored in the plunger during the pumping stroke. Y

Another object ofthe invention is to provide for operating a pluralityof work de vices from the same motor and causing the work devices tocontrol the operation of each other.

This invention accordingly is disclosed in the embodiment thereof shownin the accompanying drawings and comprises the features of construction,the combination of elements,

. and lthearrangement of parts which will be exemplified in thestructure hereinafter set forth, and the scope of the application ofwhich will be indicated in the claims.

Referring-to the drawings, Figure 1 is a -view in elevation, and partlyin section, of a plunger type pumping system constructed in accordancewith the present invention;

Fig. 2 is a cross-sectional view in elevation of a coupling shown inFig. 1; and

Fig. 3 is a plan view of the pumping 'system shown in Fig. 1 with theaddition of other apparatus to form a complete system embodied in thepresent invention.

Referring to Fig. 1 of the drawings, apparatus embodying the presentinvention may be applied to an oil well having the usual string ofcasing 1 suspended therein, the lower end of the casing terminating atthe point near the strata of oil bearing sand 2.

In order to lift the iuid from the strata of oil bearing sand to thesurface of the ground, a plunger pump is provided comprising a string ofpump tubing 3 within the casing 1 and a working barrel or pump cylinder4 to which is attached a perforated strainer 5 for admitting oil orother liquid, and excluding sand from the working barrel 4.

In order to raise the iuid which enters the working barrel 4, a plunger6 with a ball valve 7 is provided and disposed to be reciprocated withinthe working barrel 4 by means of a string of pump rods 8. attached to apolish rod 9 which extends through a suitable stuling box 11.

The usual type of standing valve 12 is provided in the lower extremityof the working barrel 4 to permit the iuid to enter the pump barrel 4and to prevent a return iow of Huid from the barrel 4 during thedownward stroke of the plunger.

As will be observed from the drawings, a second string of well casing 14extends from the surface to a point near the working barrel 4 where itis coupled to the tubing 3 by means of a reducer coupling 15.

The constructional details of the coupling 15 are shown in Fig. 2. Theupper end of the tubing 3 is attached to the lower reduced end of thecoupling 15 at 16` making" a gas or liquid tight joint. The upper end ofthe coupling is provided with screw-threads at 17, disposed to engagethe threaded portion of the well casing 14 and is also provided with acylindrical seat 18 to receive the lower Unthreaded end of the tubing 3.The lower portion of the tubing 3 contains a 'plurality of perforations,shown at 19 to afford communication from the tubing 3 into the casing14.

The auxiliary casing 14 is provided with a cap 21 at its upper end whichis provided with a suitable packing through which the tubing 3 passes.As shown, this particular construction forms an annular space betweenthe casing 14 and tubing 3 that is utilized to retain as or air underpressure, as will be referred to in greater detail hereinafter.

Natural gas or air under pressure may be admitted to the casing 14through a pipe 22 and valve 23, which are secured to the casing cap 21by means of the flange coupling 24. A pressure gauge 25 is provided for4indicating the gas or air pressure within the casing The pump tubing 3,which extends through the stufiing box in the casing cap 21 is providedwith a cap 26 which is adapted to support the stuiiing box 11. The fluidwhich is raised by the plunger 6, or by the combined action of theplunger and compressed air or gas, is discharged from the cap 26 throughthe valve 27 and pipe 28 into any suitable receptacle such, for example,as a tank or an oil gathering line.

A pipe nipple which connects the valve 27 to the tubing cap 26 is tappedto receive an air vent pipe'29 that is provided with a controlling valve31, the purpose of which will be described in detail'hereinafter.

In order to impart a reciprocating motion to the pump plunger 6, thepolish rod 9 is connected to a rotatable drum 32 by means of a exiblecable or wire line 33 which passes over a sheave wheel 34. The sheavewheel 34 may be supported in any convenient manner such, for example, asby an ordinary well derrick or by any other suitable structure.

In order to aotuate the drum 32, a suitable motor driven reduction gearmechanism 35 is provided, together with suitable control vvthat aredisposed to engage the sprocket wheels 41 and 42, rotatably mounted onthe shaft 36.

In order to hold the hoist drum 32 in any desired position whenvthe pumpis not in operation friction brake bands 43 are provided. The operationof the bands 43 may be controlled in any desired manner such, forexample, as by a well known manually operated lever system or anelectromagnetic control.

The sprocket 41 is connected by a chain 44 to the driving sprocket 45 ofthe gear mechanism 35. In this embodiment of the invention, the gearmechanism shown, is a modified form of the well known double drivedifferential type that is used for earth .of bevel sun-gear wheels 46and 47, rotatboring and the like, and isladapted for single motoroperation. The gear mechanism 35 comprises a pair ably mounted on ashaft 49. A spur gear 51 1s securely keyed to the sun gear 46 and 1sdisposed to mesh with the driving p1n1on 52 which is mounted upon thedrive shaft 53. The sunar wheels 46 and 47 are each provided wit anextended sleeve portion which serves as quill bearings surroundmg theshaft 49 and are rotatably supported in suitable bearings in the gearcase 54, as shown. The sleeve portion of the sun gear 47 is extendedbeyond the gear case 54 to receive the sprocket 55 which is securely keed thereon. v

he planetary element of the differential mechanism comprises spider 56,and a plug rality of bevel pinion wheels 57 rotatably mounted on pinionshafts 58 and disposed to -mesh with the sun-gear wheels 46-and 47.

The spider 56 is secured to the shaft 49 which is rotatably mounted inthe sleeve extensions of the sun-gear Wheels 46 and 47. In order tocontrol the operation of the differential planetary element or spider56, the shaft 49 1s rovided with a friction brake 59.

n this embodiment of the invention, the prime mover for driving the gearmechanism 35 is an induction motor 61 of the squirrel cage type and isconnected to the pinion shaft 53 by `the coupling 62. The motor 61 isdisposed to be connected to a power source such as conductors 63, bymeans of a switch 64 andl an auto-starter 65.

In order to control the operation of the planetary element 56 of thedifferential gear mechanism 35, to obtain rotation of the drum 32 in thedesired manner to reciprocate the pump plunger 6 a work device 66 isprovided. As shown the driving sprocket wheel 68 of the work device 66is connected for operation to the gear 35 by means of a chain 67. Thework device 66 may be a pump for handling the Huid raised from the wellor a compressor for forcing gas under ressure into the annular space'formed by t e casing 14 and tubing 3, each of which, operating as acontrol device, will be described in detail hereinafter.

The discharge of t-he work device 66, is controlled by a three-wayrotary valve 69.

Since valves of this type are well known inv the art, a detailed view ofthis lparticular .piece of apparatus has not been shown.

However, the valve comprises an outer box or case, having an inletopening and two discharge openings threaded to receive pipe. The case isbored to receive a rotatable cylinder member with ports and passagesarranged so that by rotating -the cylinder vin one direction, the inletwill communicate with one discharge opening and close the otherdischarge opening, and, by rotating the valve in the opposite direction,the first mentioned discharge opening is closedand the second mentionedopening is connected to aii'ord communication with the inlet.

It will be readily understood that by utilizing a control device such asthe'rotary valve 69 the Work device 66 may be loaded j to such an extentas to cause the'sun-gear wheel 47 of the gear mechanism 35 to remainstationary or run very slowly depending upon the amount of load imposedupon the planetaryelement 56 by the hoisting drum 32. Vhen the motor 61is rotating at a substantially constant speed in one directionv only,the planetary element '56 will rotate in the same directlon if the sungear 47 is stationary or rotating at a slower speed than the drivensun-gear Wheel 46, which will operate the hoist drum 32 and thereforethe pump plunger. Under the same operating conditions for, the motor,if' the sun-gear' wheel 47 is permitted to rotate reducing the load onthe work device 66, the planetary element 56 will be reversed by theweight of the pumping' string and conse uently 'permits the drum 32 tounwind until t e pump plunger reaches the bottom of its stroke.

It is therefore apparent that by automatically. controlling vthedischarge and consequently the loading' of the work device 66 inaccordance with the number of drum rota;-

aov

tions, the pump plunger will be eriodically to state that it comprises adriven gear train which upon a certain predetermined number ofrevolutions in either direction of rotation, causes a second element 'tobe automatically revolved a partial revolution. The second element hasconsiderable momentum and, therefore, is capable of exerting acomparatively high turning torque which may be utilized to operate amotor controller or a valve mechanism such as described hereinbefore.

As shown, the torque shaft upon which r the sprocket, 72 is secured isconnected to the operating sprocket 73 of the three-way valve 69 bymeans of a chain 74.

The operation of the oscillator 71 is effected by connecting the geartrain actuating sprocket 75 to the drum sprocket 42 by means of a chain76. The ratio of one sprocket to that of the other being such as toallow a suflicient number of drum revolutions to make a complete pumpingstroke before the torque shaft and sprocket 72 of the oscillator 71 isactuated to reverse the rotary 4valve 69.

It will be observed that the intake port of the rotary valve 69 isconnectedto the dis'- charge port of the work device 66 by means of apipe 77 and controlling valve 78.

A pressureV gauge 79 is provided for indicating the discharge pressureof the uid or gas through the pipe 77. rIlhe pressure readings of thegauge 79 will also indicate the pull on the chain 67 and on the Wireline or cable 33 which will serve as an indirect measurement of theweight supported by the wire line 33 `during pumping or hoistingoperations. l

It is to be understood that the invention as shown and described issuitable for pumping a well by either a mechanical lift method or by a.combination mechanical lift and gas or air lift method as v hereinbeforedescribed, and, in addition, without change or modification the systemmay be utilized to perform the necessary' hoisting operations such, forexample, as hoisting rods and tubing or making repairs which may requirethe use of hoisting equipment.

The operation of the system will first be described when operating as acombination mechanical pumping lift and gas lift system. In this event,the work device 66 is assumed to be a compressor forl supplying gas orair under pressure to the casing 14. The intake of the compressor 66,which is controlled by the valves 81 and 96, may be connected to anysuitable source of natural gas supply such as tank 95, valve 81 beingkept closed. One of the discharge ports of the rotary valve 69 isconnected to the casing cap 21, through the valve 85, T 86, pipes 87, 88and 22. It will be observed that the T 86 in the discharge line isconnected to a pressure tank 89, through pipe 91 and pressure controlValve 92 and that the other discharge port of the rotary valve 69 isconnected to the pressure tank 89 through the valve 93 and pipe 94.

In order to set the system in operation, the clutches 38 and 39 aremoved to the illustrated or disengaged positions, which allows thesprockets 41 and 42 to rotate freely on the drum shaft 36. The drum 32is held in a fixed position by operating the brake band 43to the holdingposition. The motor 61 may then be set in operation by closing theswitch 64 and operating the auto-star` er 65 in the usual manner. Sincethe sprocket 55, which is actuated by the sun gear 47, is connected tothe compressor, the load thereon is greater than the friction load ofthe sprocket 41, which is connected to the sprocket 45 by means of thechain 44, and therefore, the planetary ele' ment 56 of gear mechanism 35will revolve freely and no power will be transmitted to the compressor.

In order to set the compressor in operation, the brake 59 on the shaft49 is actuated to its holding position, and stops the movement of theplanetary element 56, and power from the motor 61 is transmitted to thecompressor through the pinion 52, ear wheel 51, sun gear 46, planetarypinions 5 ,sun gear 47, sprocket 55, and chain 67 to the sprocket 68 onthe compressor crank shaft.

Since it is necessary to impose a heavy load upon the compressor 66 toeilect the operation of the hoisting drum 32 as hereinbefore described,the compressor intake valve 96, discharge valves 78 and 93 are openedand the rotary. valve 69 positioned by hand to discharge through valve93 into the pressure tank 89.

The operation of the compressor 66 is con tinued in`this manner untilthe pressure in the tank 89 increases to the required amount which is ahigher pressure than that required within the casing 14. The rotaryvalve 69 is then rotated by hand soas to permit the compressor 66 todischarge through the valve 85 and pipes 87, 88 and 22 into the wellcasing 14. When the pressure within the casing 14 rises to a certainpredetermined value the reducing valve 92 which controls the dischargefrom the high pressure tank 89 is released and therefore the quantity ofgas supplied to the casing 14 is also increased. It will be readilyunderstood that since the dicharge from the high pressure tank 89 iscontrolled by the existing pressure in the well casing 14 acomparatively slow discharge through the valve 92 will take place solong as the casing pressure does not fall below a certain value; alsothat the consequent pressure reduction in the tank 89 will not be greatenough to'relieve the load upon the compressor 66 to such an extent asto prevent operation of the drum 32 as hereinbefore described.

In order to set the drum 32 in operation to actuate the pump plunger 6.the clutch 38 is closed to engage the sprocket 41, and the drum brakes43 and 59 are released. Since the compressor 66 is discharging against alow'pressure head in the casing 14, the planetary element 56 cannotrevolve to operate the drum 32 as the power required to hoist thepumping string, comprising the plungerv 6 and rods 8, is greater thanthe compressor load. Therefore, in order to load the compressor therotary valve 69 is rotated by hand to again discharge into the tank 89which causes the sun gear 47 to slow down and ultimately stop when thecompressor load becomes greater than the pump load.

When the speed of the driven sun-gear wheel 46 becomes greater than thespeed of the sun-gear wheel 47 which revolves in opposite direction, theplanetary element 56 will revolve in accordance with the well knownaction of the diiferential.

Power is then transmitted through the planetary shaft 49. sprocket 45,chain 44 to the 'driving sprocket 41 of the hoist drum 32. The operationof the hoist drum 32 will raise the pump plunger 6 until it reaches omit the planetary element 56 to revolve in a reverse direction, beinglreversed by the power transmitted throng the drum 32 by the Weight ofthe pumping string. Since the energy stored by the pumping string duringthe upward stroke reaches a high value the power transmitted backthrough the plantetary element 56 is applied directly to the sun-gearwheels 46 and 47 and therefore the sun-gear wheel 47 is driven at aspeed controlled by the load at the compressor 66.

It will be readily understood that by regulating the discharge of thecompressor 66 by ad]usting the valve 85 the descending speed of thepumping string can be controlled as desired.

When the pumping string reaches the bottom of the stroke the oscillator71 is operated and consequentl the rotary valve 69 is actuated to againdirect the discharge of the compressor 66 into the high pressure tank 89which immediately causes the planetary element 56 to revolve and hoistthe pump plunger 6 in the same manner as hereinbefore described.

It will be apparent that the operation of the well pump may becontrolled by utilizing work device 66 as a reciprocating pump insteadof as a compressor 66. In this event the pump 66 is shown connecteddirectly to the casing cap 21 through pipes 82, 83, 84 and 22 and valve23.

In operating the system, the motor 61 and ump 66 are set in operation asdescribed Eereinbefore with the hoisting drum 32 held in a fixedposition by the brake 43. It will be readily understood that a quantityof iiuid must be supplied for controlling the operation of the pump 66until the Well pump or plunger 6 has operated long enough to lift theiiuid in the well to the surface. The

pump 66 is, therefore, connected to the storage tank 95, through thevalve 96 as shown. In this instance, the tank 95 contains a supply ofliquid, preferably oil and by closing valves 81, 85 and 93, openingvalves 78 and 90 and by positioning the rotary valve 69 to dischargethrough the valve 90.and pipe 97, a circulating system is provided forthe pump.

In order to set the hoist drum 32 in operation, the brakes 43 and 59 arereleased and the clutches 38 and 39 actuated to the closed position.Discharge of the pump 66 is then restricted by moving the rotary valve69 to close the port communicating with valve 90 and pipei 97, which asdescribed hereinbefore causes the planetary element 56 vwhich drives thedrum 32 to revolve and actuate the pump plunger 6 to the top of itsstroke. WhenA the pump plunger 6 reaches the top of the upward strokethe oscillator 71 actuatesl the rotary valve 69 to permit the pump 66 todisch-arge through the circulating system as described herein-before andthe planetary element 56automatically reverses to permit the downwardstrokeof the plunger 6.

The descending speed of the -plunger 6 is also controlled in thisinstance by regulating the discharge of the pump 66 by means o the valve90.

The operation of the system continues in this manner until the fluidwhich is being raised from the well reaches the surface as evidenced bydischarge through the vent valve 31, in which case the intake ort of thepump 66 is connected to the casing cap 21 by opening the valves 23 and8l. Since the iuid in the storage tank 95 is no longer required forcontrolling the operation of the pump-66, the valve 96is closed, andtherefore the fluid from the well is pumped directly into the storagetank 95.

It will be readily understood that the operation and control of the pumpl66 will be the same as described hereinbefore, the pump now receivingfluid from the well instead of from the tank 95 and dischargin undercontrol of the rotary valve 69 into t e storage tank 95 or into anyother suitable receptacle, such as storage tank 89 as by opening valve93. Furthermore, opening valves 27 and 92 will permit the well fluid toilow through tubing cap 26 into tank 89.

It will be readily understood that the system as shown may be utilizedat any time to perform hoisting operations, such for example as removingthe rods or tubing from the well, by using the fluid in the tank 95 forcontrolling the operation ofthe pump 66 as'hereinbefore described indetail. However, in this instance the discharge of the pump 66 iscontrolled by positioning the rotary valve 69 to discharge through thevalve 90 and pipe 97, with the oscillator 71 disconnected from the drum32, and then alternately opening and closing the valve 90 to obtainlowering and hoisting operation of the drum 32.

It will be apparent that in operating the system as set forthhereinbefore, the kinetic energy of the descending pump stringcomprising the rods 8 and plunger 6, will be transmitted through thereduction gear mechanism 35 to the motor 61, as well as to the workdevice 66. This will tend to overspeed the motor 61 thereby providing aregenerative braking action which will limit the motor speed and returnelectrical energy to the power circuit.

From the foregoing explanation it will be apparent that a pumping systemis provided wherein an ordinary plunger pump such as is commonly usedfor pumping oil wells and the like, is operated in accordance with thebest practice, by utilizing an auxiliary work device for controlling theoperation of the pump and in addition for doing useful work such forexample as tpumping fluid or compressing gas or air or various uses.Since the principle of the invention is such as to utilize the enerstored in the moving parts of the pump or operatin the auxil- 1ary workdevice the eiciency o the system as a whole is high, which is a verydeslrable feature.

While the illustrated example constitutes a practical embodiment of myinventionLI do not limit myself to the exact details herein illustrated,since modifications of the system can be made without departin from thespirit of the invention as define in the appended claims.

I claim as my invention:

1. In a well pumping system, the combination of: two concentric wellcasings, an intermediate coupling for the outer of said casings, saidcoupling being arranged to receive the lower end of the inner casing andto provide a common fluid chamber for both said casings, a pump disposedin said outer casing below said coupling and actuated by a source ofpower at the top of the well, and means connected to the upper end ofone of said casings for forcing compressed gas through the last namedcasing into the aforesaid chamber.

2. In a well pumping system the combination of: two concentric wellcasings packed fluid tight against each other at the top of the Well andhaving unrestricted fluid communication with each other at the lower endof the inner of said casings, a mechanically Operated pump disposed inthe outer casing below the inner casing for lifting the well fiuid insaid casings, said pump being operatively connectedgto power drivenmechanism at the top yof the well, a motor for operating said mechanism,and means connected to the upper end of "one of said casings forforcingcompressed gas through said casings.

3. In a pumping system, in combination, a well casing, mechanicallyoperated pumping means disposed in the casing, pressure pumping meansfor assisting the mechanica ly operated pumping means in lifting iiuidfrom the casing, a motor for supplying energy to said pumping means, andintermittently actuated means for jointly controlling the action of themechanically operated pumping means and the pressure pumping means.

4. In a^pumping system, in combination, a well casing, mechanicallyoperated pumping means disposed in the casing, pressure pumping meansfor assisting the mechanically operated pumping means in lifting fluidfrom the casing, a motor for supplying energy to' said pumping means,power transmission means connected between the motor and themechanically operated pumping means, and means actuated in accordancewith the operation of said mechanically operated pumping means forcontrolling the operation of the power transmission means and thepressure pumping means.

5. In a system for pumping oil from wells in combination, a mechamcallyoperated pump provided with a plunger, a motor for actuating the pump, acompressor for delivering compressed fluid, means for utilizing themotor for actuating the compressor during a pumping stroke, means forutilizing the pump plunger for operating the compressor on the downstroke, and means for delivering the compressed fluid into the well tocooperate in the pumping operations.

6. In a pumping system, in combination, a well casing, a plunger pumpdisposed in the casing, a motor for operating the plunger pump, meansinterposed between the pump and motor, for controlling the operation ofthe pump, said control means including a hoisting drum for operating thepump and a differential gear mechanism for contr/lling the operation ofthe hoistin drum, and means operatively connected wlth the differentialgear mechanism for compressing and forcing lifting fluids into the wellcasing, said means being disposed to control the operation of the gearmechanism to effect the operation of the pump.

7. In a pumping system, in combination, a well casing, a plungerpump-disposed in the casing, a motor for operating the plunger pump,means interposed between the pump and motor, for controlling theoperation of the pump, said control means including a hoisting drum foroperating the pump and a dierential gear mechanism for controlling theoperation of the hoisting drum, a compressor connected in the pumpingsystem for forcing compressed lifting fluid into the well casing andmeans disposed to control the discharge of said compressor and therebyeffect the operation of the dierential gear mechanism for actuating theplunger pump.

8. In a pumping system, in combination, a Well casing, a plunger pumpdisposed in the casing, a motor for operating the plunger pump, meansinterposed between the pump and motor, for controlling the operation ofthe pump, said control means including a hoisting drum for operating thepump and a differential gear mechanism for controlling the opera-tion ofthe hoisting drum, a compressor connected in the pumping system forforcing compressed lifting fluid into the Well casing and means actuatedin accordance with the rotating of the hoisting drum disposed to varythe discharge of the compressoi` thereby varyino' its load to effect theoperation of the diqbrential gear mechanism for actuating the plun erpump.

In testimony whereo I have hereunto subscribed my name this 21st day ofFebruary,

FREDERo W. HILD.

